Diagram of Presentations Wave Particle Duality and the Quantum (Bohr) Atom (Dr. Steven Blusk) Particle Discoveries in Cosmic Rays and Accelerators (Dr. Tomasz Skwarnicki) Making Sense of everything - The Standard Model (Dr. Marina Artuso) The Instruments and Techniques of Discovery: Particle Accelerators and Detectors (Dr. Sheldon Stone) We urge you to make inquiries as we advance.. These slides will be posted on the web soon !

And then there was a problemâ¦ In the mid 20 th century, a few impacts were watched which couldn\'t be comprehended utilizing the wave hypothesis of light. Two of the more compelling perceptions were: 1) The Photo-Electric Effect (~1905) 2) The Compton Effect (1923)

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Photoelectric Effect (I) What on the off chance that we attempt this ? Shift wavelength, altered plentifulness No Yes, with low KE No Yes, with high KE No âClassicalâ Method Increase vitality by expanding abundancy electrons radiated ? electrons transmitted ? No electrons were discharged until the light\'s recurrence surpassed a basic recurrence, and soon thereafter electrons were transmitted from the surface! Light acting like a molecule with E ïµ 1/l

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Photo-Electric Effect (II) âLight particleâ Before Collision After Collision In the last âquantum-mechanicalâ picture, the light\'s vitality molecule (photon) must conquer the coupling vitality of the electron to the core. On the off chance that the photon\'s vitality surpasses the coupling vitality , the electron is transmitted with a KE = E photon â E tying . The photon\'s vitality is given by E = h n = hc/l, where the consistent h = 6.6x10 - 34 [J s] is Planckâs steady.

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Photons In Quantum hypothesis light is made out of individual quanta (or wave bundles) called photons. As indicated by quantum hypothesis , every photon has a vitality given by E = h n = hc/l h = 6.6x10 - 34 [J s] Planckâs steady , 10 photons have a vitality equivalent to ten times a solitary photon. The photoelectric impact can\'t be comprehended by means of a Wave Picture. We must view light as made out of particles, every conveying vitality and force.

The Compton Effect Incident X-beam wavelength l 1 M A T E R Scattered X-beam wavelength l 2 l 2 > l 1 e Electron comes flying out In 1924, A. H. Compton performed an analysis where X-beams encroached on matter, and he gauged the scattered radiation. Issue: According to the wave picture of light, the episode X-beam ought to surrender some of its vitality to the electron, and develop with a lower vitality ( i.e., the sufficiency is lower), however ought to have l 2 =l 1 . It was found that the scattered X-beam did not have the same wavelength ?

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Quantum Picture to the Rescue Electron at first very still (practically) Scattered X-beam E 2 = h c/l 2 Incident X-beam E 1 = h c/l 1 l 2 > l 1 e Compton found that in the event that you regard the photons as though they were particles of zero mass, with vitality E=hc/l and energy p=h/l ï¨ The crash carries on pretty much as though it were 2 particles impacting ! Photon carries on like a molecule with vitality & force as given above!

How would we see ? Light reflects (or photons disseminate ) from a surface and achieves our eye. Our eye/mind shapes a picture of the article.

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Wavelength versus Size But imagine a scenario in which we need to âseeâ littler things, similar to inside a molecule, or inside the core, or even inside a nucleon ???. Indeed, even with a noticeable light magnifying instrument, we are restricted to having the capacity to determine objects which are at any rate around: 10 - 6 [m] = 1 [ m m] = 1000 [nm] in size . This is on the grounds that obvious light, with a wavelength of ~500 [nm] can\'t resolve protests whose size is littler than itâs wavelength .

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Matter Waves ? âIf light can act like a molecule, may particles act like waves â? Louis de Broglie The short answer is YES. The clarification lies in the vulnerability\'s domain standard & quantum mechanics, Particles, similar to photons, likewise have a wavelength given by: l = h/p = h/mv That is, the wavelength of a molecule relies on upon its energy, much the same as a photon! The principle contrast is that matter particles have mass, and photons donât !

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Electron Microscope The electron magnifying instrument utilizes the wave conduct of electrons to make pictures which are generally undiscernable for obvious light! This picture was brought with a Scanning Electron Microscope ( SEM ). These gadgets can resolve components down to around 1 [nm]. This speaks the truth 100 times superior to should be possible with noticeable light magnifying lens! Imperative POINT HERE : High vitality particles can be utilized to uncover the structure of matter !

Scattering Experiments In 1911, Rutherford set out to test this speculation. Alpha molecule source an Around ~1900, the iota\'s structure was not known. Basic speculation was that it was similar to a plum-pudding Calculations, in light of the known laws of power and attraction demonstrated that the substantial alpha particles ought to be just marginally avoided by this âplum-puddingâ atomâ¦ Ernest Rutherford 1871-1937 Awarded the Nobel Prize in 1908 The computations recommended that an insignificant division of the alpha particles ought to be scattered by more than 90 o .

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Au Contraire an a Contrary to desires, Rutherford found that an altogether expansive division (~1/8000) of the alpha particles â ricocheted back â in the same bearing in which they came â¦The figuring, in light of the plum-pudding model, was that less than 1/10,000,000,000 ought to do this ??? Gold foil In Rutherfordâs wordsâ¦ âIt was an incredible most inconceivable occasion that ever transpired in my life. It was as though you shot a 15-inch maritime shell at a bit of tissue paper and the shell returned right and hit you.â Huh ???

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The (main) understanding an a The molecule must have a strong center fit for conferring substantial electric strengths onto an approaching (charged) molecule .

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Neils Bohr and the Quantum Atom Circa 1913 Pointed out difficult issues with Rutherfordâs iota Electrons ought to emanate as they circle the core, and in doing as such, lose vitality, until they winding into the core. Particles just transmit quantized measures of vitality (i.e., as saw in Hydrogen spectra) 1885-1962 He hypothesized Awarded the Nobel Prize in 1922 Electric power keeps electrons in circle Only certain circles are steady , and they don\'t emanate vitality Radiation is discharged when an e - bounced from an external circle to an internal circle and the vitality contrast is emitted as a radiation.

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Bohrâs Picture of the Atom Before After Radiated photon n = Electron in most reduced âallowedâ vitality level (n=1) 5 4 3 2 1 Electron in energized state (n=5) Electron tumbles to the least vitality level Allowed Orbits Electrons circle the core because of the Electric power Note : There are numerous more vitality levels past n=5, they are excluded for effortlessness

James Chadwick and the Neutron 4 2 a + 9 4 Be 12 6 C + 1 0 n Circa 1925-1932 Picked up where Rutherford left off with additionally dissipating experimentsâ¦ Performed a progression of disseminating examinations with a - particles 1891-1974 Awarded the Nobel Prize in 1935 Applying vitality and energy protection he found that the mass of this new question was ~1.15 times that of the proton mass. Chadwick proposed that the emanant radiation was from another, unbiased molecule , the neutron.

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This finished the photo, or did itâ¦ Electrons had been think about since ~1900 (J. J. Thomson et al ) By ~1932 Collisions of alpha particles with matter gave us the photo that the molecule has a thick center at itâs focus made out of protons & neutrons. The basic units of matter are protons, neutrons and electrons.